Further evidence for CCN aerosol concentrations determining the height of warm rain and ice initiation in convective clouds over the Amazon basin

Ramon Campos Braga; Daniel Rosenfeld; Ralf Weigel; Tina Jurkat; Meinrat O. Andreae; Manfred Wendisch; Ulrich Poeschl; Christiane Voigt; Christoph Mahnke; Stephan Borrmann; Rachel I. Albrecht; Sergej Molleker; Daniel A. Vila; Luiz A. T. Machado; Lucas Grulich

doi:10.5194/acp-17-14433-2017

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Further evidence for CCN aerosol concentrations determining the height of warm rain and ice initiation in convective clouds over the Amazon basin

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Further evidence for CCN aerosol concentrations determining the height of warm rain and ice initiation in convective clouds over the Amazon basin

Ramon Campos Braga, Daniel Rosenfeld, Ralf Weigel, Tina Jurkat, Meinrat O. Andreae, Manfred Wendisch, Ulrich Poeschl, Christiane Voigt, Christoph Mahnke, Stephan Borrmann, …

Atmospheric chemistry and physics, Vol.17(23), pp.14433-14456

05/12/2017

DOI: https://doi.org/10.5194/acp-17-14433-2017

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We have investigated how aerosols affect the height above cloud base of rain and ice hydrometeor initiation and the subsequent vertical evolution of cloud droplet size and number concentrations in growing convective cumulus. For this purpose we used in situ data of hydrometeor size distributions measured with instruments mounted on HALO aircraft during the ACRIDICON-CHUVA campaign over the Amazon during September 2014. The results show that the height of rain initiation by collision and coalescence processes (D-r, in units of meters above cloud base) is linearly correlated with the number concentration of droplets (N-d in cm(-3)) nucleated at cloud base (D-r approximate to 5 . N-d). Additional cloud processes associated with D-r, such as GCCN, cloud, and mixing with ambient air and other processes, produce deviations of similar to 21% in the linear relationship, but it does not mask the clear relationship between D-r and N-d, which was also found at different regions around the globe (e.g., Israel and India). When N-d exceeded values of about 1000 cm(-3), D-r became greater than 5000 m, and the first observed precipitation particles were ice hydrometeors. Therefore, no liquid water raindrops were observed within growing convective cumulus during polluted conditions. Furthermore, the formation of ice particles also took place at higher altitudes in the clouds in polluted conditions because the resulting smaller cloud droplets froze at colder temperatures compared to the larger drops in the unpolluted cases. The measured vertical profiles of droplet effective radius (r(e)) were close to those estimated by assuming adiabatic conditions (r(ea)), supporting the hypothesis that the entrainment and mixing of air into convective clouds is nearly inhomogeneous. Additional CCN activation on aerosol particles from biomass burning and air pollution reduced r(e) below r(ea), which further inhibited the formation of raindrops and ice particles and resulted in even higher altitudes for rain and ice initiation.

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Title: Further evidence for CCN aerosol concentrations determining the height of warm rain and ice initiation in convective clouds over the Amazon basin
Creators: Ramon Campos Braga - National Institute for Space Research
Daniel Rosenfeld - Hebrew University of Jerusalem
Ralf Weigel - Johannes Gutenberg University Mainz
Tina Jurkat - German Aerospace Center
Meinrat O. Andreae - Max Planck Institute for Chemistry
Manfred Wendisch - Meteor
Ulrich Poeschl - Max Planck Institute for Chemistry
Christiane Voigt - German Aerospace Center
Christoph Mahnke - Johannes Gutenberg University Mainz
Stephan Borrmann - Johannes Gutenberg University Mainz
Rachel I. Albrecht - Universidade de São Paulo
Sergej Molleker - Max Planck Institute for Chemistry
Daniel A. Vila - National Institute for Space Research
Luiz A. T. Machado - National Institute for Space Research
Lucas Grulich - Johannes Gutenberg University Mainz
Publication Details: Atmospheric chemistry and physics, Vol.17(23), pp.14433-14456
Publisher: Copernicus Gesellschaft Mbh
Number of pages: 24
Grant note: FP7-603445 / project BACCHUS, European Commission 01LG1205A / German Federal Ministry of Education and Research (BMBF, Bundesministerium fur Bildung und Forschung) within the joint ROMIC project SPITFIRE VO1504/4-1; JU 3059/1-1; DFG SPP 1294 HALO / German Science Foundation; German Research Foundation (DFG) FAPESP (Sao Paulo Research Foundation); Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) FP7-AAT-2012-3.5.1-1 / EU project HAIC SPP 1294 / German Science Foundation (Deutsche Forschungsgemeinschaft, DFG) within the DFG Priority Program; German Research Foundation (DFG) ACRIDICON-CHUVA campaign by the Max Planck Society Brazilian funding agency CNPq; Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPQ) German Aerospace Center (DLR); Helmholtz Association; German Aerospace Centre (DLR) Brazilian funding agency CAPES; Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)
Identifiers: 991013093610702368
Academic Unit: Faculty of Science and Engineering
Language: English
Resource Type: Journal article

Further evidence for CCN aerosol concentrations determining the height of warm rain and ice initiation in convective clouds over the Amazon basin

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